Hitherto, for example, in order to electrically connect a movable part and a fixed part of a stepper of a semiconductor manufacture apparatus, a flat-shaped cable such as a flat cable is used, and in this flat-shaped cable, from the viewpoint of excellent electric characteristics such as a low dielectric constant, or heat resistance, chemical resistance or out gas measure, a PTFE sheet or an EPTFE sheet is used as an insulator or a sheath. The flat-shaped cable in which the PTFE sheet or the EPTFE sheet is used as the insulator or the sheath as stated above is formed in such a manner that for example, as disclosed in U.S. Pat. No. 3,082,292, transmission lines, such as conductors or coaxial cables, are supplied into respective grooves of a grooved compression roll having the many grooves, the many transmission lines, such as the conductors or coaxial cables, are arranged in parallel to each other, PTFE sheets or EPTFE sheets are also supplied from both sides of these supplied conductors or transmission lines, and these conductors or transmission lines are covered with and held between the PTFE sheets or the EPTFE sheets (insulating layers or sheaths) from both the sides, and then, the PTFE sheets or the EPTFE sheets at both the sides of the conductors or transmission lines are sintered at a sintering temperature of 327° C. or higher by a high temperature sintering bath (baking furnace) or the like, so that they are joined and formed.
In the flat-shaped cable formed in this way, various problems have arisen when the PTFE sheets or the EPTFE sheets are sintered by the high temperature sintering bath. That is, there are problems that since the PTFE sheets or the EPTFE sheets are shrunken at the time of the sintering, it is difficult to keep a distance (pitch) between the respective conductors of the flat-shaped cable or between the transmission lines with necessary accuracy, or since the PTFE sheets or the EPTFE sheets are hardened by the sintering, the bendability, flexibility, pliability or slidability of the flat-shaped cable becomes inferior.
Besides, since the flat-shaped cable is influenced by the high temperature of the sintering bath when the PTFE sheets or the EPTFE sheets are sintered, although there is no problem in the case where the conductor (soft copper) is silver plated or nickel plated, in the case where the conductor (soft copper) is tin plated, there is a case where the color of the conductor (soft copper) is changed, disconnection becomes liable to occur, and it can not be used as the cable.
Besides, in the flat-shaped cable, such as a flat cable, in which the PTFE sheets or the EPTFE sheets are used as the insulators or the sheaths as stated above, in the case where many coaxial cables or multi-core cables, as the transmission lines, are arranged side by side to form the flat-shaped cable, when the PTFE sheets or the EPTFE sheets are sintered by the high temperature sintering bath, in the case where the coaxial cables are used, the center conductor of the coaxial cable can kink, and as a result, there can occur a problem in electric characteristics, such as poor voltage resistance or poor characteristic impedance, and there can arise a problem that disconnection also becomes liable to occur.